> ## Documentation Index
> Fetch the complete documentation index at: https://circle-devdocs-test-ai-codegen-component.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# CCTP Block Confirmations V1

> Block confirmation requirements for attestations by chain

<Warning>
  **This is CCTP V1 version. For the latest version, see [CCTP](/cctp)**.
</Warning>

Before signing an attestation for a source chain event, Circle waits for a
specified number of onchain block confirmations to achieve
<Tooltip tip="The point at which a transaction is fully finalized on-chain and can no longer be reversed or reorganized. This ensures the highest level of security and certainty before attestation. Hard Finality requires the transaction to reach full consensus on the source blockchain, typically resulting in longer processing times.">hard finality</Tooltip>.

The table below shows the average time required for an attestation to become
available after a message is emitted onchain.

<Note>
  **Note:** These values are subject to change.
</Note>

## CCTP V1 Attestation Times

| Source Chain    | Number of Blocks  | Average Time         |
| --------------- | ----------------- | -------------------- |
| **Ethereum**    | \~65\*            | \~13 to 19 minutes\* |
| **Avalanche**   | 1                 | \~8 seconds          |
| **OP Mainnet**  | \~65 ETH blocks\* | \~13 to 19 minutes\* |
| **Arbitrum**    | \~65 ETH blocks\* | \~13 to 19 minutes\* |
| **Noble**       | 1                 | \~20 seconds         |
| **Base**        | \~65 ETH blocks\* | \~13 to 19 minutes\* |
| **Polygon PoS** | \~33              | \~75 to 120 seconds  |
| **Solana**      | 32                | \~25 seconds         |
| **Sui**         | 1                 | \~8 seconds          |
| **Aptos**       | 1                 | \~8 seconds          |
| **Unichain**    | \~65 ETH blocks\* | \~13 to 19 minutes\* |

<Note>
  **Block confirmations for L2s to Ethereum**

  Layer 2 (L2) blockchains publish transaction data in batches to Ethereum L1,
  and the frequency of these posts varies by chain. Some submit batches every
  few minutes, while others are less frequent. After a batch is posted, Circle
  waits for the Ethereum L1 block containing the batch to finalize, which
  typically happens after \~65 blocks, or 13 to 19 minutes, before issuing an
  attestation.
</Note>

<br />

**WHAT'S NEXT**

* [CCTP Chain Domains V1 <Icon icon="arrow-right" />](/cctp/v1/supported-domains)